Computer systems, from small handheld electronic devices to medium-sized mobile and desktop systems to large servers and workstations, are becoming increasingly pervasive in our society. A typical computer system includes two or more integrated circuits (ICs) affixed to a printed circuit board (PCB). The ICs communicate with one another by sending signals across transmission lines formed on the PCB. For example, one IC may be a processor while one or more other ICs are memory devices that the processor accesses to store and retrieve data. Increasing the speed, or frequency, at which signals are sent across these transmission lines tends to increase the computational power of the computer. Unfortunately, there are electrical properties that limit the signal frequency.
Inductance, resistance, and capacitance on the transmission lines not only limit the frequency but also introduce noise into the signals. Noise may be compensated for by allowing more time for each bit of the signal to settle on the transmission line before the next bit is sent, thereby further reducing signal frequency.
In an effort to overcome some of these limitations, most ICs include input-output (I-O) buffers. An I-O buffer conditions a signal driven to and received from another IC. A typical I-O buffer conditions an output signal generated by the IC by boosting the signal's voltage or current levels before driving the signal on the transmission line. This boosted signal may then be transferred to another IC via the transmission line more cleanly. The I-O buffer may condition an input signal received from another IC via the transmission line by adjusting the signal's voltage or current levels before providing the signal to other circuitry within the IC. The I-O buffer may additionally provide electrostatic discharge protection for the IC.